In short, climate change has reduced the intensity / frequency of cold extremes averaged over time. (washingtonpost.com)
-- It is virtually certain that increases in the frequency of warm daily temperature extremes and decreases in cold extremes will occur throughout the 21st century on a global scale. (dotearth.blogs.nytimes.com)
Scientists call this a decrease in temperature variance, and it implies fewer temperature extremes, in this case notably fewer cold extremes. (theconversation.com)